FIGS. 1 and 2 are photographs showing measurement methods using conventional theodolite and measuring pole, and FIG. 3 is photographs showing a measurement method using a conventional GPS measuring instrument.
Generally, the measurement in a civil construction site, is carried out by means of a theodolite 1000 and a GPS receiver 51, as will be discussed later.
1. Measurement Method Using Theodolite
A measurement method using a theodolite includes the steps of: (a) allowing a center point of the theodolite 1000 to correspond to a coordinate point (reference point, CP) of the ground as an instrument point at which the theodolite 1000 is installed; (b) leveling the theodolite 1000; (c) collimating back collimation to set an azimuth angle; (d) locating a measuring pile at an arbitrary point to obtain a new reference point CP; (e) locating a measuring pole 1100 to which a prism and a circular bubble (level) are coupled at a center point of the measuring pile to perform the leveling of the circular bubble by means of a tripod and tongs attached to the tripod; (f) obtaining the azimuth angle and a distance value through the theodolite 1000; and (g) obtaining the coordinate of the reference point CP through the azimuth angle and the distance value.
A method for setting out an observation point (a center line of a road, alignment of curbs, and center of manhole) includes the steps of: (a) locating a theodolite at an instrument point to set the azimuth angle of the observation point; (b) aligning the center of a measuring pole to the line collimated by the set azimuth angle; (c) performing leveling through a level; (d) obtaining a distance value using the theodolite; and (e) repeatedly adjusting the measuring pole forwardly and backwardly in a direction of the collimated line in accordance with the result of the distance value.
2. Measurement Method Using GPS Measuring Instrument
A measurement method using a GPS measuring instrument includes the steps of: (a) coupling a GPS receiver 51 to a measuring pole 1100; (b) locating a measuring pile at an arbitrary point to obtain a reference point CP; (c) installing the measuring pole 1100 to which the GPS receiver 51 is attached on a center point of the measuring pile; (d) leveling a circular bubble (level) attached to the measuring pole 1100 by means of a tripod and tongs attached to the tripod; and (e) obtaining the coordinate of the reference point CP through the GPS receiver 51.
A method for setting out an observation point includes the steps of: (a) selecting the observation point (a center line of a road, alignment of curbs and so on) from a controller screen; (b) allowing the observation point to approach a target point using the distance from the target point and the movement to an arrow direction indicated on the controller screen; (c) leveling the GPS measuring instrument; and (d) repeatedly moving the GPS measuring instrument to the target point in the arrow direction to determine the observation point.
However, the conventional measurement methods have the following problems.
In case of the conventional method for measuring the reference point CP through the theodolite 1000, first, the measuring pole 1100 is located at the observation point and after the circular level is leveled by using the tripod and the tongs attached to the upper portion of the tripod, the azimuth angle and distance are measured by means of the theodolite 1000 to obtain the coordinate of the reference point CP.
At this time, errors may be generated according to the distance between the ground and the prism due to the height of the measuring pole 1100, and also, artificial errors may be generated from the step where the circular level is leveled through the tongs manipulated by an auxiliary measurer.
In case of the conventional measurement for the observation point, further, after the azimuth angle of the observation point is collimated through the theodolite and the center of the measuring pole moves to left and right sides and accurately corresponds to the line of collimation, a difference value between the value of the distance observed and the value of the distance of the observation point is aligned to the observation point (a center line of a road, alignment of curbs and so on) through the forward and backward movements of the center of the measuring pole along the line of collimation. In this case, however, since the azimuth angle and distance of the observation point are fixed, the measurement is carried out through the repetition of the above-mentioned processes, thereby undesirably requiring a long period of time for measurement. Due to the errors on the height difference of the measuring pole between the ground and the prism, the errors generated according to the degree of skill of the auxiliary measurer, and the errors generated from the sensitivity of the circular level attached to the measuring pole, further, it is impossible to find an accurate observation point.
In case of the conventional method for measuring the reference point CP through the GPS receiver, a tribrach 1200 and the measuring pole 1100 are located at the observation point to obtain the coordinate of the reference point CP.
If the tribrach 1200 is used, precision becomes improved, but after the reference point CP above the ground corresponds to the center of the tribrach 1200, the tribrach 1200 should be leveled by using the legs of a tripod 1300 to minimize the movements of the reference point CP and the center of the tribrach 1200 corresponding to each other. Accordingly, the misaligned reference point CP and the center of the tribrach 1200 have to be aligned to each other by means of the unfastening of coupling screws between the tripod 1300 and the tribrach 1200, and next, the leveling steps are repeatedly carried out to align the reference point CP and the center of the tribrach 1200 through the lower screws of the tribrach 1200, thereby undesirably requiring a long period of time for measurement.
If the measuring pole to which the GPS receiver is attached is used, the measuring speed becomes improved, but after the measuring pole is located at the observation point to level the circular level attached to the measuring pole by means of the tripod for fixing the measuring pole and the tongs attached to the upper portion of the tripod, the coordinate of the reference point is produced on the controller screen. At this time, there are errors on the height difference of the measuring pole between the ground and the prism, the errors generated according to the degree of skill of the auxiliary measurer, and the errors generated according to the viewing angles of the circular level attached to the measuring pole.
In case of the conventional measurement for the observation point using the GPS measuring instrument, further, the measuring pole having an upper portion to which the GPS receiver is attached moves near the observation point and then moves to the accurate position of the observation point by using the information (distance, direction, and arrow) on the observation point (a center line of a road, alignment of curbs and so on) indicated on the controller.
Due to the errors on the height difference between the ground and the GPS receiver and the errors generated according to the degree of skill of the auxiliary measurer, however, there are limitations in the reduction of the errors caused upon the measurement of the observation point through the existing measuring equipment (theodolite, GPS measuring instrument, prism, measuring pole and so on).